U.S. Pat. No. 4,456,829, assigned to the assignee hereof, discloses electro-optical apparatus for measuring distance to a relatively moving surface, such as distance to a road surface from a vehicle frame of reference passing thereover. The apparatus includes a light transmitter for projecting a rectangular beam vertically downwardly onto the road surface. A rotating scanner includes a circumferential array of facets for sequentially receiving an image diffusely reflected from the road surface and reflecting such image through a rectangular reticle onto a photodetector. Reference beams are sequentially reflected by the road image-reflecting scanner facets onto a reference detector. Distance to the road surface is determined as a function of the angle of incidence of the road image onto the scanner by comparing the time of incidence of the road image to the times of occurrence of the reference reflections on the reference detector. In the exemplary but preferred road-surface implementation, road surface profile is sampled and stored at successive increments of vehicle displacement as indicated by an encoder or the like coupled to a vehicle wheel.
Although the apparatus disclosed in the noted patent has enjoyed substantial commercial acceptance and success, improvements remain desirable in a number of respects. For example, it is desirable to eliminate any necessity for moving parts, such as the rotating scanner and drive motor. Furthermore, the plurality of light sources and detectors in the patented apparatus increase complexity and expense, both at the time of manufacture and during use when mechanical adjustments must be maintained. An object of the present invention, therefore, is to provide a sensor of the described character having no moving parts, and in which adjustments are substantially reduced or eliminated.
A more general object of the present invention is to provide non-contact distance measuring apparatus which embodies improved economy, reliability and accuracy in assembly and use, and which finds particular utility in the measurement of road profile. In furtherance of the foregoing, a more specific object of the invention is to provide an improved electro-optical scanner and system for measuring the profile of a relatively moving surface, such as a road surface.